Juncins G and H: New briarane diterpenoids of the Indian Ocean gorgonian Junceella juncea Pallas

Chemical examination of the Indian Ocean gorgonian, Junceella juncea furnishes two new diterpenoids of the briarane skeleton, juncin G, 1 and juncin H, 3 along with the antipodal derivatives of known gemmacolides A, 4 and B, 2. The structures of juncin H and G are shown to be (1S,2S,6S,8R,9S,10S,11R,12R,14R,17R)-6-chloro-11,20-epoxy-14-(3- methylbutanoyl)-2,9-12-triacetoxy-8-hydroxybriar-5(16)-en-18,7- olide and (1S,2S,6S,9S,10S,12R,13R,14R)-6-chloro-13-(3-methylbuatanoyl)-2,9,12,14-tetraacetoxybriaran-4,8(17)-dien-18,7-olide, respectively, by a comparative study of their spectral data. For the first time, three polyhydroxy sterols 6-8 are also isolated from this species.